Water Intoxication: A Possible Complication During Endurance Exercise☆

A century of exercise physiology: concepts that ignited the study of human thermoregulation. Part 3: Heat and cold tolerance during exercise

In this third installment of our four-part historical series, we evaluate contributions that shaped our understanding of heat and cold stress during occupational and athletic pursuits. Our first topic concerns how we tolerate, and sometimes fail to tolerate, exercise-heat stress. By 1900, physical activity with clothing- and climate-induced evaporative impediments led to an extraordinarily high incidence of heat stroke within the military. Fortunately, deep-body temperatures > 40 °C were not always fatal. Thirty years later, water immersion and patient treatments mimicking sweat evaporation were found to be effective, with the adage of cool first, transport later being adopted. We gradually acquired an understanding of thermoeffector function during heat storage, and learned about challenges to other regulatory mechanisms. In our second topic, we explore cold tolerance and intolerance. By the 1930s, hypothermia was known to reduce cutaneous circulation, particularly at the extremities, conserving body heat. Cold-induced vasodilatation hindered heat conservation, but it was protective. Increased metabolic heat production followed, driven by shivering and non-shivering thermogenesis, even during exercise and work. Physical endurance and shivering could both be compromised by hypoglycaemia. Later, treatments for hypothermia and cold injuries were refined, and the thermal after-drop was explained. In our final topic, we critique the numerous indices developed in attempts to numerically rate hot and cold stresses. The criteria for an effective thermal stress index were established by the 1930s. However, few indices satisfied those requirements, either then or now, and the surviving indices, including the unvalidated Wet-Bulb Globe-Thermometer index, do not fully predict thermal strain.

Ultra-Endurance Participation and Acute Kidney Injury: A Narrative Review

Increasingly popular, ultra-endurance participation exposes athletes to extremely high levels of functional and structural damage. Ultra-endurance athletes commonly develop acute kidney injury (AKI) and other pathologies harmful to kidney health. There is strong evidence that non-steroidal anti-inflammatory drugs, common amongst ultra-athletes, is linked to increased risk and severity of AKI and potentially ischaemic renal injury, i.e., acute tubular necrosis. Ultra-endurance participation also increases the risk of exertional rhabdomyolysis, exercise-associated hyponatremia, and gastrointestinal symptoms, interlinked pathologies all with potential to increase the risk of AKI. Hydration and fuelling both also play a role with the development of multiple pathologies and ultimately AKI, highlighting the need for individualised nutritional and hydration plans to promote athlete health. Faster athletes, supplementing nitrates, and being female also increase the risk of developing AKI in this setting. Serum creatinine criteria do not provide the best indicator for AKI for ultra-athletes therefore further investigations are needed to assess the practicality and accuracy of new renal biomarkers such as neutrophil gelatinase-associated lipocalin (NGAL). The potential of recurring episodes of AKI provide need for further research to assess the longitudinal renal health impact of ultra-participation to provide appropriate advice to athletes, coaches, medical staff, and event organisers.

Ultra-endurance events in tropical environments and countermeasures to optimize performances and health

Physical performance in a tropical environment, combining high heat and humidity, is a difficult physiological challenge that requires specific preparation. The elevated humidity of a tropical climate impairs the thermoregulatory mechanisms by limiting the rate of sweat evaporation. Hence, a proper management of whole-body temperature is required to complete an ultra-endurance event in such an environment. In these long-duration events, which can last from 8 to 20 h, held in hot and humid settings, performance is tightly linked to the ability in maintaining an optimal hydration status. Indeed, the rate of withdrawal in these longer races was associated with lower water intake, and the majority of finishers exhibited alterations in electrolyte balance (e.g., sodium). Hence, this work reviews the effects on performance of high heat and humidity in two representative ultra-endurance sports, ultramarathons and long-distance triathlons, and several countermeasures to counteract the impact of these harsh environmental stresses and maintain a high level of performance, such as hydration, cooling strategies and heat acclimation.

Peso corporal e estado hídrico de triatletas no Ironman Brasil: Um fator de correção

INTRODUÇÃO: O triatlo Ironman é uma prova de longa duração em que comumente se observam alterações hidroeletrolíticas. A desidratação e hiponatremia são prevalentes e o diagnóstico diferencial entre elas deve levar em conta a variação de peso corporal do atleta. Contudo, deve-se considerar também que as variações são um somatório de fontes hídricas e não hídricas, sendo necessário aplicar um fator de correção para avaliação do real estado hídrico do atleta. Objetivo: Avaliar o estado hídrico do atleta baseado nas variações de peso corporal sem e com aplicação de fator de correção.MÉTODO: Vinte e seis atletas foram pesados em três momentos distintos (dois dias antes da prova, imediatamente antes e após a realização). O estado hídrico foi classificado com base no cálculo da variação percentual de peso corporal isolado e com aplicação do fator de correção de 1 kg proporcional ao atleta de 70 kg. Além disso, foram registrados os principais sinais clínicos e sintomas referidos.RESULTADOS: Nas 48 horas que antecederam a largada houve um ganho médio de peso de 1,2 kg. Após a prova, vinte e três (88,4%) atletas foram classificados como desidratados inicialmente, porém após a aplicação do fator de correção à variação do peso, esse número caiu para 12 (46,1%). Dos classificados como desidratação severa houve redução de 7 (26,2%) para nenhum atleta. Dez atletas (3,8%) apresentaram sinais e sintomas de desidratação.CONCLUSÃO: A classificação do estado de hidratação baseado nas perdas hídricas durante a prova foi significativamente modificado pela aplicação do fator de correção, sendo sua utilização justificada pelas evidências de que o ganho de peso nas 48 horas anteriores à prova está possivelmente relacionado ao acúmulo muscular de glicogênio e água (fontes não hídricas intravasculares).

Dano muscular e perfil imunológico no triatlo ironman Brasil

INTRODUÇÃO: O triatlo Ironman se caracteriza por ser uma atividade de longa duração em que alterações orgânicas agudas estão presentes. OBJETIVO: verificar a ocorrência de dano muscular e sua relação com o perfil imunológico em triatletas do Ironman - Brasil. MÉTODOS: A amostra de sangue foi obtida de 21 atletas em três momentos: dois dias antes da prova (pré), imediatamente após a prova (pós) e seis dias após a prova (seis dias pós), em que foram analisadas de forma isolada as variáveis creatinoquinase (CK), os leucócitos totais, linfócitos, subtipos de linfócitos CD4+ e CD8+, e relação CD4+/CD8+ e a correlação da CK como marcador de dano muscular, com as demais variáveis. RESULTADOS: As diferenças significativas foram observadas nos leucócitos pré (média: 6.242,9 mm³; DP: 1.233,3) e pós (média: 18.398,1 mm³; DP: 3.904,0; p < 0,0001); pós (média: 18.398,1 mm³; DP: 3.904,0) e seis dias pós (média: 6.396,4 mm³; DP: 1.299,8; p < 0,0001); CK pré (média: 173,2 U/l; DP: 103,7) e pós (média: 2.339,4 U/l; DP: 1.729,0; p < 0,0001), CK pré (média: 173,2 U/l; DP: 103,7) e seis dias pós (média: 368,1 U/l; DP: 274,4; p < 0,0053); CK pós (média: 2.339,4 U/l; DP: 1.729,0) e seis dias pós (média: 368,1 U/l; DP: 274,4; p < 0,0003); CD4+/CD8+ pré (média: 1,9; DP: 0,8) e seis dias pós (média: 2,4; DP: 1,1: p < 0,00032). CONCLUSÃO: Houve dano muscular no período pós-prova imediato e melhora do perfil imunológico após o sexto dia.

Nutrition for adventure racing

Adventure racing requires competitors to perform various disciplines ranging from, but not limited to, mountain biking, running, kayaking, climbing, mountaineering, flat- and white-water boating and orienteering over a rugged, often remote and wilderness terrain. Races can vary from 6 hours to expedition-length events that can last up to 10-consecutive days or more. The purpose of this article is to provide evidence-based nutritional recommendations for adventure racing competitors. Energy expenditures of 365-750 kcal/hour have been reported with total energy expenditures of 18 000-80 000 kcal required to complete adventure races, and large negative energy balances during competitions have been reported. Nutrition, therefore, plays a major role in the successful completion of such ultra-endurance events. Conducting research in these events is challenging and the limited studies investigating dietary surveys and nutritional status of adventure racers indicate that competitors do not meet nutrition recommendations for ultra-endurance exercise. Carbohydrate intakes of 7-12 g/kg are needed during periods of prolonged training to meet requirements and replenish glycogen stores. Protein intakes of 1.4-1.7 g/kg are recommended to build and repair tissue. Adequate replacement of fluid and electrolytes are crucial, particularly during extreme temperatures; however, sweat rates can vary greatly between competitors. There is considerable evidence to support the use of sports drinks, gels and bars, as they are a convenient and portable source of carbohydrate that can be consumed during exercise, in training and in competition. Similarly, protein and amino acid supplements can be useful to help meet periods of increased protein requirements. Caffeine can be used as an ergogenic aid to help competitors stay awake during prolonged periods, enhance glycogen resynthesis and enhance endurance performance.

Nutrition for adventure racing

Adventure racing requires competitors to perform various disciplines ranging from, but not limited to, mountain biking, running, kayaking, climbing, mountaineering, flat- and white-water boating and orienteering over a rugged, often remote and wilderness terrain. Races can vary from 6 hours to expedition-length events that can last up to 10-consecutive days or more. The purpose of this article is to provide evidence-based nutritional recommendations for adventure racing competitors. Energy expenditures of 365-750 kcal/hour have been reported with total energy expenditures of 18 000-80 000 kcal required to complete adventure races, and large negative energy balances during competitions have been reported. Nutrition, therefore, plays a major role in the successful completion of such ultra-endurance events. Conducting research in these events is challenging and the limited studies investigating dietary surveys and nutritional status of adventure racers indicate that competitors do not meet nutrition recommendations for ultra-endurance exercise. Carbohydrate intakes of 7-12 g/kg are needed during periods of prolonged training to meet requirements and replenish glycogen stores. Protein intakes of 1.4-1.7 g/kg are recommended to build and repair tissue. Adequate replacement of fluid and electrolytes are crucial, particularly during extreme temperatures; however, sweat rates can vary greatly between competitors. There is considerable evidence to support the use of sports drinks, gels and bars, as they are a convenient and portable source of carbohydrate that can be consumed during exercise, in training and in competition. Similarly, protein and amino acid supplements can be useful to help meet periods of increased protein requirements. Caffeine can be used as an ergogenic aid to help competitors stay awake during prolonged periods, enhance glycogen resynthesis and enhance endurance performance.

Marathon runner with acute hyponatremia: a neurological disorder

We report the case of an athletic 49-year-old female who has run the 2011 Marathon of Paris and was addressed to the hospital for a confusion. The investigations revealed a cerebral edema complicating a severe hyponatremia secondary to an exercise-associated hyponatremia (EAH). Using 3% hypertonic saline solution, the evolution the patient rapidly improve allowing discharge after 7 days. We then discuss the importance of EAH in long-term efforts.